PROJECT SUMMARY/ABSTRACT The 4th International Symposium on Collaterals to the Brain is a multidisciplinary scientific conference focused on collateral circulation in ischemic stroke. This proposal requests partial support for a conference with broad, long-term objectives that will advance current research on collateral blood flow and identify gaps in current treatment strategies around the world. The collaterome, or individual capacity to offset ischemia in the brain, and determination of a favorable collateral profile have become pivotal factors in the consideration of cerebral ischemia and the precision medicine of stroke driving individualized medical decision-making. The conference directly addresses the most pressing issues and gaps in optimally defining collateral status that limit realization of stroke therapies around the world. Decisive challenges include generalizability of optimal triage and selection paradigms based on collateral status for definitive treatment of ischemic stroke, rapid dissemination of expert methods and transformative advances, and the urgent need to leverage networking opportunities for stroke education and science related to the hemodynamics of collaterals to the brain. The aims of this conference will convene over 50 invited faculty from around the world to connect on-site participants at the state-of-the-art facility with remote audiences in more than 35 countries and regions. The confirmed program of this 2-day conference is structured into 40-minute sessions devoted to key issues in translating the collaterome in stroke therapy across the globe. The interspersed networking opportunities will enhance collaborative initiatives in this burgeoning field and rapid dissemination of electronic posters, proceedings and other publications will intensify the impact of this unique and esteemed annual Symposium. Dedicated efforts for appropriate representation have been delineated to have parity in the numbers of women, recruit underrepresented minorities and persons with disabilities. Measurable outcomes will quantify the impact of this symposium on the NINDS mission to enhance knowledge of collaterals and reduce the burden of neurological disease due to stroke. This unique forum of expertise extending from a state-of-the-art venue across the world emphasizes the timely impact of collaterals on a monumental scale, encouraging maximal participation, rapid diffusion and added value of networking resource.